In a cellular system, the Radio Network Controller, RNC, is connected to the Radio Base Station, RBS, via the so called Transport Network, TN. In all cellular systems, and in particular in a cellular system which is enabled for HSPA, High Speed Packet Access, the TN is a potential bottleneck, both in the downlink, DL, and in the uplink, UL, direction.
RFC 3135 (available at www.rfc-archive.org) describes the use of performance enhancing proxies in order to improve degraded TCP performance.